Incandescent electric lamp



e HoLs'r INCANDESCENT ELECTRIQ LAN? Filed March 11. 1927 Inventor: GLIIes Holst,

y Mfg;

Hus Attorney.

Patented Jan. 10, 1928.

UNITED STATES PATENT OFFICE.

GILLES HOLST, 0F EINDHOVEN, NETHERLANDS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

INCANDESCENT Application filed March 11, 1927, Serial No. 174,626, and in the Netherfands April 10, 1926.

The invention relates to incandescent electric lamps, and more particularly 1noandescent lamps in which the absorption of light is reduced by means of a substance usually called a getter, which has the property of transforming the tungsten vaporized from the filament'into a material which absorbs less light. Many chemical substances, such as sodium chloride, cryolite, potassium thallo chloride and calcium fluoride, have been used as getters. A getter such as calcium fluoride may be applied to the filament, for example, by spraying or ,dipping before the stem is sealed into the bulb of the incandescent lamps After the lamp is sealed in and exhausted, the filament is heated and the getter evaporates from the filament and precipitates on the inside of the lamp bulb as a transparent or translucent layer. Other getters, such as potassium thallo-chloride, may be applied at a certain spot inside the incandescent lamp where the temperature is high enough to cause the getter to dissociate slightly, giving 05 chlorine, which combines with the vaporized tungsten to transform it lnto a transparent salt.

One object of this invention is to make incandescent electric-lamps and similar de vices to be made in such a way that the activity of the getter can be regulated at actly in accordance with the amount or" tun sten which evaporates during each unit of time at the filament temperature at which the lamp is designed to operate.

According tothe invention the incandescent electric lump or similar device is pro vided with an auxiliary electrode carrying a getter which becomes active, as by generai; ing gas, under the influence of an electrical discharge between the auxiliary electrode and the tilanieut, and while active causes the formation with the evaporated material the filament of transparent chemical com" initiations or compounds.

When the incandescent lamp is lighted, there will generally be parts of the filament which have a negative potential with respect to the auxiliary electrode, and consequently-a discharge of electrons will. ilow from these parts of the filament, so that the auxiliar electrode will be hitby electrons emitted y these or? the filament. "Un der the influence of this electron bombardmeat the getter on or associated with the auxiliary electrode will be activated, as, for example, by being dissociated, thereby generating a gas which forms with the evaporated tungsten transparent or translucent chemical compounds, and thereby counteracts the absorption of light which would occur if the vaporized-tungsten deposited unchanged onthe walls of the bulb.

Preferably, the auxiliary electrodeis connected conductively to one of the terminals of the filament. either directly or through a resistance, and is so located with reference to the filament that the total quantity of tungsten which evaporates at normal filament temperature during each unit of time will chemicallycombine with the gas generated by the getter during the same unit of time. In accordance with a construction which has given very favorable results in practice, a considerable portion. of the auxiliary electrode is adjacent a portion of the filament, in some cases surrounding a certain part of the filament like a spiral, and is connected to one of the leading-in wires through a resistance it necessary.

The drawing shows one form of incandescent electric lamp constructed according to the invention. The filament 1 is a coiled tungsten wire connected to the leads or terminals 2 and 3, which are joined to the leading-in wires 4 and the press 6 of the stem of the lamp. A part of the filament is adiacent an auxiliary electrode 7, which may be in the shape of a large coil surrounding the filament. The elec trode 7 is associated with, and may be covered by a getter, and is connected so as to he of positive potential with reference to the adjacent portion of the filament. as hy being conductively connected to the lead 2. if required, a resistor may be inserted in the circuit between the lead 2 and the auxiliary electrode 7, and may be installeddn the base oi the lamp. By suitably selecting the part of the filament which is adjacent to or is surrounded by the auxiliary electrode *Z, the potential difference between this part of the filament and the auxiliary electrode, and consequently the effect of theelectron bombardment, and the resultant activity of i the getter, may be regulated as desired.

met I claimv as new anddesire to secure by Letters Patent of the United States, is, 1. lln a device of the character described,

the combination of a sealed. envelope, lead 5, hermetically sealed into Zlllil ing-in wires extending through the walls of said envelope, a filament secured to said lead wires, and an auxiliary electrode connected to act as an anode to a portion of said filament and provided with a material which in response to an electrical discharge to said electrode evolves a gas which forms with the vaporized material of said filament a compound more transparent than said vaporized material.

2. An incandescent lamp comprising a sealed envelope containing a filament and an auxiliary electrode provided with a getter decomposable by an electrical discharge and mounted in such relation to a portion of said filament that at normal operating temperature'of said filament an electrical discharge to said auxiliary electrode causes said getter to evolve a chemically active atmosphere at a rate so related to the rate of vaporization of the filament material that all said vaporized filament material is converted by said atmosphere into translucent compounds as fast as it vaporizes.

3. An incandescent lamp having a sealed envelope containing a filament, and an auxiliary electrode coated with a getter rendered active by an electrical discharge to said electrode, said electrode being connected to one terminal of said filament and mounted in eeaeoa such relation to a part of said filament having a potential diflering from that of said terminal that an electrical discharge occurs between said electrode and said part of the filament during operation of the lamp.

4. An incandescent lamp having a sealed envelope containing a filament, and an auxiliary electrode coated with a getter rendered active by an electrical discharge to said electrode and connected to one terminal of said filament, said electrode being coiled and surrounding, a part of said filament at a potential during operation of the lamp different from the potential of said terminal.

5. In a device of the character described, 1

the combination of an evacuated envelope, a filament in said envelope, current supply means for said filament, and an auxiliary electrode which evolves gas in response to an electrical discharge to it cent a portion of said filament, said electrode bem connected to said current su ply means to it} at a potential difierent'i rom the potential of said adjacent portion of said filament.

In witness whereof, I have hereunto set my7hand this seventeenth day of February, 192

GILLES HOLST.

and mounted adja- 

